Start der Blüte

After the first long dark cycle it's in flower. Once a particular hormone produced in the dark has enough time to accumulate to sufficient levels, it's a 'switch' inside the plant. This is 100% about length of uninterrupted darkness, hence the importance not to have light leaks in flower phase. 10+ hours has teh potential to start flower. There is some variation as to how much any 1 plant needs to enter flower, which is why people use 12/12 - it safely covers all related genetic variety.